Synthesis and Structural Characterization of a Monofunctionalized Phloroglucin-Derivative: A Precursor for Heterotrinuclear meta-Phenylene Bridged Complexes

Glaser, Thorsten; Heidemeier, Maik; Krickemeyer, Erich; Bögge, Hartmut

doi:10.1515/znb-2006-0616

Cited by 3 publications

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“…This is an additional piece of evidence, that there must be some kind of driving force for the dimerization of two trinuclear triplesalen complexes as has already been observed in [(talen t-Bu 2 )Cu II 3 ] 15 and [(talen t-Bu 2 ){Fe III (MeOH)(H 2 O)} 3 ] 3+ . 30 We assume that close van der Waals contacts of the tert-butylbenzene subunits support energetically this dimerization to supramolecular aggregates. The formation of [Mn III 6 ] 3+ has to be considered for the synthesis of the heptanuclear complexes [Mn III 6 M] n+ , in which the product of the reaction of H 6 talen t-Bu 2 with Mn II acetate is treated with a hexacyanometallate.…”

Section: Discussionmentioning

confidence: 92%

“…15 Also, two [(talen t-Bu 2 ){Fe III (MeOH)(H 2 O)} 3 ] 3+ units dimerize and encapsulate the uncommon [Cl ◊ ◊ ◊ H ◊ ◊ ◊ Cl]unit. 30 An advantage of the ligand folding in the trinuclear complexes [(talen t-Bu 2 ){M(solv) n } 3 ] m+ is the pre-organization of the three metal ions for coordination of three facial nitrogen atoms of a hexacyanometallate [M(CN) 6 ] n-. Thus, reaction of the molecular building block [(talen t-Bu 2 ){Mn III (solv) n } 3 ] 3+ -formed in situ by reaction of H 6 talen t-Bu2 with Mn II acetate-with [Cr(CN) 6 ] 3and [Fe(CN) 6 ] 3resulted in the formation of the heptanuclear complexes [{(talen t-Bu 2 )Mn III 3 } 2 {Cr III (CN) 6 }] 3+ ([Mn III 6 Cr III ] 3+ ) 31 and [{(talen t-Bu 2 )Mn III 3 } 2 {Fe III (CN) 6 }] 3+ ([Mn III 6 Fe III ] 3+ ), 32 respectively.…”

Section: Introductionmentioning

confidence: 99%

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A MnIII triplesalen-based 1D pearl necklace: exchange interactions and zero-field splittings in a C₃-symmetric Mn^III₆complex

et al. 2010

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The reaction of the tert-butyl-substituted triplesalen ligand H(6)talen(t-Bu(2)) with 2.8 equivalents of Mn(OAc)(2) x 4 H(2)O in MeOH in the presence of NaBPh(4) results in the formation of the one-dimensional (1D) coordination polymer {[{(talen(t-Bu(2)))Mn(3)(MeOH)}(2)(mu(2)-OAc)(3)](mu(2)-OAc)}(n)(BPh(4))(2n) ({[Mn(III)(6)](OAc)}(n)(BPh(4))(2n)) which has been characterized by FTIR, elemental analysis, ESI-MS, single-crystal X-ray diffraction and magnetic measurements. The triplesalen ligand (talen(t-Bu(2)))(6-) provides three salen-like coordination compartments bridged in a meta-phenylene arrangement by a phloroglucinol backbone resulting in the trinuclear Mn(III) base unit {(talen(t-Bu(2)))Mn(3)}(3+). Two of these base units are bridged by three inner acetate ligands giving rise to the hexanuclear complex [{(talen(t-Bu(2)))Mn(3)(MeOH)}(2)(mu(2)-OAc)(3)](3+) ([Mn(III)(6)](3+)). These complexes are bridged by a single external acetate to form a 1D chain as pearls in a pearl necklace. Variable temperature-variable field and mu(eff)vs. T magnetic data have been analyzed in detail by full-matrix diagonalization of the appropriate spin-Hamiltonian consisting of isotropic exchange, zero-field splitting, and Zeeman interaction taking into account the relative orientation of the D-tensors. Satisfactory reproduction of the experimental data have been obtained for parameters sets J(1) = -(0.60 +/- 0.15) cm(-1), J(2) = -(1.05 +/- 0.15) cm(-1), and D(Mn) = -(3.0 +/- 0.7) cm(-1) with J(1) describing the exchange through the phloroglucinol backbone and J(2) describing the exchange through the inner acetates. The non-necessity to incorporate the bridging outer acetates correlates with the longer Mn-O bonds. The experimental data can neither be analyzed without incorporating zero-field splitting nor by the application of a single effective spin ground state.

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Section: Discussionmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

A MnIII triplesalen-based 1D pearl necklace: exchange interactions and zero-field splittings in a C₃-symmetric Mn^III₆complex

et al. 2010

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“…124,125,127,129,130 We applied several of these methods for the synthesis of a triplesalen ligand and obtained various new compounds. 131 The successful synthesis of a triplesalen ligand is based on an observation of Elias and coworkers. 127 They reported that the sterically more crowded amine function of diamine I (Scheme 4) does not react with ketones to form ketimines, but only with aldehydes to form aldimines.…”

Section: Ligand Synthesismentioning

confidence: 99%

Rational design of single-molecule magnets: a supramolecular approach

2011

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Since the discovery that Mn(12)OAc acts as a single-molecule magnet (SMM), an increasing number of transition metal complexes have been demonstrated to behave as SMMs. The signature of a SMM is a slow relaxation of the magnetization at low temperatures accompanied by a magnetic hysteresis. The origin of SMM behaviour is the existence of an appreciable thermal barrier U for spin-reversal called magnetic anisotropy barrier which is related to the combination of a large total spin ground state (S(t)) and an easy-axis magnetic anisotropy. The extensive research on Mn(12)OAc and other SMMs has established more prerequisites for a rational development of new SMMs besides the high-spin ground state and the magnetic anisotropy: the symmetry should be at least C(3) to minimize the quantum tunneling of the magnetization through the anisotropy barrier but lower than cubic to avoid the cancellation of the local anisotropies upon projection onto the spin ground state. Based on these prerequisites, we have designed the ligand triplesalen which combines the phloroglucinol bridging unit for high spin ground states by the spin-polarization mechanism with a salen-like ligand environment for single-site magnetic anisotropies by a strong tetragonal ligand field. The C(3) symmetric, trinuclear complexes of the triplesalen ligand (talen(t-Bu(2)))(6-) exhibit a strong ligand folding resulting in an overall bowl-shaped molecular structure. This ligand folding preorganizes the axial coordination sites of the metal salen subunits for the complementary binding of three facial nitrogen atoms of a hexacyanometallate unit. This leads to a high driving force for the formation of heptanuclear complexes [M(t)(6)M(c)](n+) by the assembly of three molecular building blocks. Attractive van der Waals interactions of the tert-butyl phenyl units of two triplesalen trinuclear building blocks increase the driving force. In this respect, we have been able to synthesize the isostructural series [Mn(III)(6)Cr(III)](3+), [Mn(III)(6)Fe(III)](3+), and [Mn(III)(6)Co(III)](3+) with [Mn(III)(6)Cr(III)](3+) being a SMM. A detailed analysis and comparison of the magnetic properties of the three heptanuclear complexes and the tetranuclear half-unit [Mn(III)(3)Cr(III)](3+) provides significant insight for further optimization of the SMM properties. The modular assembly of the heptanuclear complexes from three molecular building blocks allows the fine-tuning of the molecular and steric properties of each building block without losing the driving force for the formation of the heptanuclear complexes. This possibility of rational improvements of our isostructural series is the main advantage of our supramolecular approach.

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Do Trinuclear Triplesalen Complexes Exhibit Cooperative Effects? Synthesis, Characterization, and Enantioselective Catalytic Sulfoxidation by Chiral Trinuclear Fe^III Triplesalen Complexes

Mukherjee

Stammler

Bögge

et al. 2010

Chemistry A European J

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The chiral triplesalen ligand H(6)chand provides three chiral salen ligand compartments in a meta-phenylene arrangement by a phloroglucinol backbone. The two diastereomeric versions H(6)chand(RR) and H(6)chand(rac) have been used to synthesize the enantiomerically pure chiral complex [(FeCl)(3)(chand(RR))] (3(RR)) and the racemic complex [(FeCl)(3)(chand(rac))] (3(rac)). The molecular structure of the free ligand H(6)chand(rac) exhibits at the terminal donor sides the O-protonated phenol-imine tautomer and at the central donor sides the N-protonated keto-enamine tautomer. The trinuclear complexes are comprised of five-coordinate square-pyramidal Fe(III) ions with a chloride at the axial positions. The crystal structure of 3(rac) exhibits collinear chiral channels of approximately 11 A in diameter making up 33.6 % of the volume of the crystals, whereas the crystal structure of 3(RR) exhibits voids of 560 A(3). Mössbauer spectroscopy demonstrates the presence of Fe(III) high-spin ions. UV/Vis spectroscopy is in accordance with a large delocalized system in the central backbone evidenced by strong low-energy shifts of the imine pi-pi* transitions relative to that of the terminal units. Magnetic measurements reveal weak intramolecular exchange interactions but strong magnetic anisotropies of the Fe(III) ions. Complexes 3(rac) and 3(RR) are good catalysts for the sulfoxidation of sulfides providing very good yields and high selectivities with 3(RR) being enantioselective. A comparison of 3(RR) and [FeCl(salen')] provides higher yields and selectivities but lower enantiomeric excess values (ee values) for 3(RR) relative to [FeCl(salen')]. The low ee values of 3(RR) appeared to be connected to a strong ligand folding in 3(RR), opening access to the catalytically active high-valent Fe-O species. The higher selectivity is assigned to a cooperative stabilization of the catalytically active high-valent Fe-O species through the phloroglucinol backbone in the trinuclear complexes.

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Synthesis and Structural Characterization of a Monofunctionalized Phloroglucin-Derivative: A Precursor for Heterotrinuclear meta-Phenylene Bridged Complexes

Cited by 3 publications

References 14 publications

A MnIII triplesalen-based 1D pearl necklace: exchange interactions and zero-field splittings in a C₃-symmetric Mn^III₆complex

A MnIII triplesalen-based 1D pearl necklace: exchange interactions and zero-field splittings in a C₃-symmetric Mn^III₆complex

Rational design of single-molecule magnets: a supramolecular approach

Do Trinuclear Triplesalen Complexes Exhibit Cooperative Effects? Synthesis, Characterization, and Enantioselective Catalytic Sulfoxidation by Chiral Trinuclear Fe^III Triplesalen Complexes

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Synthesis and Structural Characterization of a Monofunctionalized Phloroglucin-Derivative: A Precursor for Heterotrinuclear meta-Phenylene Bridged Complexes

Cited by 3 publications

References 14 publications

A MnIII triplesalen-based 1D pearl necklace: exchange interactions and zero-field splittings in a C3-symmetric MnIII6complex

A MnIII triplesalen-based 1D pearl necklace: exchange interactions and zero-field splittings in a C3-symmetric MnIII6complex

Rational design of single-molecule magnets: a supramolecular approach

Do Trinuclear Triplesalen Complexes Exhibit Cooperative Effects? Synthesis, Characterization, and Enantioselective Catalytic Sulfoxidation by Chiral Trinuclear FeIII Triplesalen Complexes

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A MnIII triplesalen-based 1D pearl necklace: exchange interactions and zero-field splittings in a C₃-symmetric Mn^III₆complex

A MnIII triplesalen-based 1D pearl necklace: exchange interactions and zero-field splittings in a C₃-symmetric Mn^III₆complex

Do Trinuclear Triplesalen Complexes Exhibit Cooperative Effects? Synthesis, Characterization, and Enantioselective Catalytic Sulfoxidation by Chiral Trinuclear Fe^III Triplesalen Complexes